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Soil Solarization

The Garden will be using Soil Solarization as a prescribed method of weed control in the Meadow Revival Project. 

Starting in September 2013, we began experimenting with both black and clear plastic in our soil solarization treatment in the upper Meadow to determine which is most effective in our climate. Larger portions of the Meadow may be solarized in the summer of 2014.

What is Soil Solarization?

  • A non-chemical method of controlling weeds and soil pathogens
  • Plastic sheets heat soil by capturing sun’s energy
  • Kills annual weeds and weed seeds, soil diseases, insect pests
  • Is less effective against deep-rooted perennials such as Bermuda grass, oxalis, and bindweed
  • Heat is greatest in top 2 inches of soil which can reach temperatures of 108-130 deg F
  • Effective in hot summer months in areas of direct sunlight
  • Populations of beneficial microorganisms may be reduced at first, but they quickly recolonize the soil

Method for Soil Solarization:

  • Use thin, clear plastic (1-2mil) which traps the most heat and is most effective in hot areas
  • In cooler, coastal zones, where solarization temperatures are harder to achieve, black plastic can be more effective because weeds can’t grow beneath it
  • Plastic should be placed flat on surface of smooth soil to avoid air pockets
  • Soil should be wet to at least 12 inches deep
  • Leave plastic in place 4-6 weeks, remove before it begins to deteriorate
  • Goal is to achieve daily temperatures of at least 110 deg F in top 6 inches of soil
  • Do not turn soil after solarization - to avoid exposing deeply buried, viable weed seeds

Additonal Resources:

Colorado State University Extension: Soil Solarization, an alternative to soil fumigants

IPM - University of California Davis: Soil Solarization for Gardens and Landscapes

Organic Gardening: Soil Solarization - Harness the sun’s power to defeat soilborne pests and pathogens